TEMPERATURE-DEPENDENCE OF THE QUENCHING OF I-STAR(2P3/2) BY I2 FROM 300-K TO 800-K

The quenching rate of I*(2P1/2) by I2 is measured over the temperature range 297-800 K by using a time-resolved diode laser absorption/gain method. The room-temperature bimolecular quenching rate constant is determined to be k(q) = (2.89 +/- 0.06) X 10(-11) cm3/(molecule.s), in good agreement with several previous determinations. The rate is found to be independent of temperature over the temperature range 300-800 K within experimental uncertainty; at 800 K the quenching rate is k(q) = (3.02 +/- 0.30) x 10(-11) cm3/(molecule.s) The temperature dependence is consistent with a quenching mechanism involving the formation of an I3 intermediate complex. The quantum yield for I* formation from the 480-nm photolysis of I2 is measured to be 0.304 +/- 0.001 at 297 K and increases slightly with temperature. This quantum yield is significantly larger than that previously determined.